In the preparation of liquid treatment compositions, it is always an aim to improve technical capabilities thereof and aesthetics. The present invention specifically relates to the aim of improving on the traditional transparent or opaque aesthetics of liquid compositions. It is also an aim of the present invention to convey the composition's technical capabilities through the aesthetics of the composition. The present invention relates to liquid compositions comprising optical modifiers that are capable of transmitting light such that the compositions appear pearlescent.
Pearlescence can be achieved by incorporation and suspension of a pearlescent agent in the liquid composition. Pearlescent agents include inorganic natural substances, such as mica, bismuth oxychloride and titanium dioxide, and organic compounds such as fish scales, metal salts of higher fatty acids, fatty glycol esters and fatty acid alkanolamides. The pearlescent agent can be acquired as a powder, suspension of the agent in a suitable suspending agent or where the agent is a crystal, it may be produced in situ.
Pearlescent agents are particulate and tend to separate from the suspension or liquid composition over time. One solution to this problem is simply to increase the viscosity of the composition. However liquid laundry or hard surface cleaning compositions necessarily have relatively low viscosity, especially at high shear, such that they may be poured. Typically a laundry composition has viscosity of less than 1500 centipoises at 20 s−1 and 21° C. Such products generally also have low viscosity at low shear, resulting in any particulates having a tendency to separate from the liquid composition and either float or settle upon storage. In either scenario this gives an undesired, non-uniform product appearance wherein part of the product is pearly and part of it is clear and homogeneous.
Another problem associated with the use of particulates, and especially pearlescent agents, in liquid laundry and hard surface cleaning applications is the likely deposition of the pearlescent agent on the surface being treated. On fabrics, especially dark fabrics, such deposits or residues can be visible with the naked eye. Moreover they may tend to draw the eye as, by their nature, they tend to sparkle in light. On dishware or hard surfaces, such as floors, deposits are equally as unappealing as they give the consumers the perception of the surface being dirty. With regard to dishware there is the added potentially issue that consumers may view the appearance of pearlescent agent on dishware as being a health issue.
Detergent compositions and pearlescent dispersions comprising pearlescent agent fatty acid glycol ester are disclosed in the following art; U.S. Pat. No. 4,717,501 (to Kao); U.S. Pat. No. 5,017,305 (to Henkel); U.S. Pat. No. 6,210,659 (to Henkel); U.S. Pat. No. 6,835,700 (to Cognis). Liquid detergent compositions containing pearlescent agent are disclosed in U.S. Pat. No. 6,956,017 (to Procter & Gamble). Liquid detergents for washing delicate garments containing pearlescent agent are disclosed in EP 520551 B1 (to Unilever).
In spite of the advances in the art, there remains a challenge to both stably suspend pearlescent agents in liquid laundry and hard surface cleaning treatment compositions and avoid the appearance of deposits or residues on the surface being treated.